A lifting sling is a structure, typically flexible, that allows a connection to be made between first and second attachment points to allow an item to be displaced or, more typically, lifted. For example, a crane may be connected to a load using a sling to allow the crane to lift the load. In this case, the first attachment point may be a hook on the end of the crane, and the second attachment point may be a hook formed by a cargo net or the like that secures the load for lifting.
Slings typically comprise at least an elongate, flexible body having end fittings connected to or formed at each end. The elongate body may be made of, as examples, fabric webbing, wire rope, chain, steel wire mesh, and/or rope round slings. The present invention is of particular significance when embodied as a rope round sling.
A rope round sling typically comprises a load bearing structure comprising load bearing material. The load bearing material typically takes the form of natural or synthetic fibers. The fibers are typically combined to form yarns, and the yarns are typically combined to form strands and/or other sub-components. The load bearing structure may thus take the form of a conventional rope structure spliced together or otherwise formed in the shape of an endless loop.
The load bearing structure is typically covered by a jacket to protect the load bearing structure from abrasion and/or potentially deleterious effects of the elements. The jacket may take the form of a fabric panel structure that is wrapped around the entire endless loop formed by the load bearing structure and secured in place. Alternatively, the jacket may take the form of a cylindrical fabric tube adapted to cover a central portion of the endless loop such that opposing portions of the endless loop form eyes that extend out of each end of the cylindrical fabric tube.
A rope round sling thus may be configured, with or without a jacket, to form first and second eyes adapted to be connected between the first and second attachment points as generally described above. To use a rope round sling in the context of a crane as described above, the crane hook will be passed through a first eye formed by a first portion of the load bearing structure and the load hook would be passed through a second eye formed by a second portion of the load bearing structure opposing the first portion. When the crane hook is raised, the load bearing structure will be placed in tension such that the load is raised with the crane hook.
The need exists for improved rope round slings that are capable of lifting increased loads for a given weight per length unit of the load bearing material.